This method is a Standard Operating Procedure (SOP) developed by CARB for the analysis of hexavalent chromium (Cr+6) in ambient air. The sample is collected using an ambient sampler which consists of a vacuum pump, calibrated rotometer, and filter holder. It is important that no metal components be present from the probe to the inlet of the sampler. The presence of metal can contaminate the sample with Cr+6.
Samples are collected on 37mm cellulose filters that have been impregnated with sodium bicarbonate which is the stabilizing agent for Cr+6. The prepared filters should be kept cool prior to use for sampling and kept in a freezer after sample collection. The filter is extracted with DI water via sonication for 3 hours and analyzed in duplicate by ion chromatography with UV-Vis detection.
The recommended collection time is 24 hours at 15 L/min. Sample collection times of less than 24 hours show predominately non-detects for Cr+6.
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| Hold Times, Preservatives, Preps, Collection, Analytical & Documentation | |
|---|---|
| Holding Time: | None specified in method. |
| Preservatives: | Keep filters cool prior to sampling. Keep filters in a freezer after collection and cool for shipment to the laboratory. |
| Required Preps: | 37mm sodium bicarbonate impregnated cellulose filters |
| Collection Method: | Ambient sampler |
| Analytical Methodology: | Ion chromatography with UV-VIS detection |
| Documentation: | 
CARB 039
|
| Analyte | Formula | CAS Number | Detection Limit | |
|---|---|---|---|---|
| Hexavalent chromium | Cr+6 |
18540-29-9 |
0.013 |
ng/cm3 |
* The analytes and detection limits listed for each method represent the typical detection limits and analytes reported for that particular method. Keep in mind that analyte lists may vary from laboratory to laboratory. Detection limits may also vary from lab to lab and are dependent upon the sample size, matrix, and any interferences that may be present in the sample.